Method of producing a device comprising flush tracks

Abstract

Title: Method for producing a device comprising flush tracks The invention relates to a method for producing a device comprising a support (10) and a metal track (20) flush with a face (100) of said support (10), said method comprising: Producing the support (10) by additive manufacturing, by providing in the support (10) a relief (12) recessed with respect to the face (100) of the support (10), Completely filling the relief (12) recessed with a metallic ink (21), Scraping the face (100) of the support (10) so as to equalize a level of metallic ink (21) in the relief (12) recessed with the face (100) of the support (10), Annealing the metallic ink (21) so as to form a metal track (20) flush with the face (100) of the support (10). Figure for abstract: Fig. 2

Description

Title of the invention: Method for producing a device comprising flush tracks Technical field

[0001] The present invention relates, in general, to a method of forming metal tracks within a support, and more particularly, to a method of metallizing a ceramic. STATE OF THE ART

[0002] Ceramic metallization processes make it possible to create metal tracks on ceramic supports.

[0003] The most direct way to form these metal tracks is to form a metal plating on the ceramic. This plating can be achieved by screen printing through a mask comprising track patterns to directly obtain the metal tracks. Alternatively, this plating can be continuously applied to the ceramic support and then engraved, for example by laser, to form the metal tracks. Other processes combining local deposition, for example by inkjet, and plating on this local deposition have also been developed. The metal tracks obtained via these processes all protrude from the surface of the ceramic support.

[0004] To improve the integration of metal tracks, the document “Wang et al., Multi-material Additive Manufacturing of LTCC Matrix and Silver Conductors for 3D, Adv Materials Technologies, 7, 2101462 (2022)” discloses a method for additive co-manufacturing of ceramic and metal tracks. This method makes it possible to obtain metal tracks that are flush with the surface of the ceramic support. This method nevertheless uses co-dispensing of materials and co-sintering that are complex to implement.

[0005] There is therefore a need for a method of producing a ceramic support comprising flush metal tracks, which is less expensive and less complex to implement.

[0006] An objective of the present invention is to meet this need and to at least partially overcome the drawbacks mentioned above.

[0007] An objective of the present invention is to propose a method for producing a device comprising a support and metal tracks flush with one face of the support, which presents an easier implementation and / or a reduced cost.

[0008] Other objects, features and advantages of the present invention will become apparent from a consideration of the following description and accompanying drawings. It is understood that other advantages may be incorporated. SUMMARY

[0009] To achieve this objective, according to one embodiment, a method is provided for producing a device comprising a support and at least one metal track flush with a face of said support, said method successively comprising: - Producing the support by additive manufacturing, by providing in the support at least one hollow relief opposite the face of the support, said at least one relief being intended to accommodate the at least one metal track, - Completely fill at least one hollow relief with metallic ink, - Scrape the face of the support so as to equalize a level of metallic ink in the at least one hollow relief with the face of the support bordering said at least one hollow relief, - Anneal the metallic ink so as to form at least one metallic track flush with the face of the support.

[0010] The support forms a mold in which the metallic ink is distributed. There is no need to use a mask or a subsequent etching step to define the metal track patterns. The support directly comprises these patterns in the form of recessed reliefs, after additive manufacturing. The support is here completely formed before filling the recessed relief(s). There is no need to manage support formation steps during filling or after filling the recessed relief with the metallic ink. Thus, the co-manufacturing and co-sintering steps taught by the document “Wang et al., Multimaterial Additive Manufacturing of LTCC Matrix and Silver Conductors for 3D, Adv Materials Technologies, 7, 2101462 (2022)” are eliminated. The method according to the invention is easier to implement.

[0011] Scraping the face of the support makes it possible to remove and / or prevent excess metallic ink overflowing from the recessed reliefs. Filling with metallic ink and scraping the support to equalize the level of this metallic ink are also inexpensive steps. The cost of the method according to the invention is reduced.

[0012] The method according to the invention advantageously makes it possible to obtain a support, typically ceramic-based, comprising metal tracks flush with the face of the support.

[0013] According to one aspect, the invention also relates to a device comprising a support, preferably ceramic-based, and metal tracks flush with one face of said support. The face of the support may typically have a curved surface. Such a device may advantageously be obtained by the method according to the invention.

[0014] Such a device can be advantageously used in the field of microelectronics or power electronics, for mounting and assembling electronic chips on the support. The invention also relates to an electronic system comprising such a device and at least one electronic chip connected to the metal tracks of the device. The flush metal tracks according to the invention are advantageously better insulated from each other thanks to the presence of the support between the sides of these “buried” metal tracks. Lateral electric arcs likely to form when the sides of the metal tracks are exposed to the air are here advantageously eliminated.

[0015] Another application of a device or support comprising protruding metallic tracks or patterns according to the invention relates to the fields of horology and jewelry. A ceramic watch dial comprising metallic indexes or marks protruding from the surface of the dial can advantageously be produced by the method according to the invention. The compactness and / or the definition of such a dial can be improved. The invention also relates to a horology or jewelry system comprising such a device. BRIEF DESCRIPTION OF THE FIGURES

[0016] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of embodiments thereof which are illustrated by the following accompanying drawings in which:

[0017] [Fig.l][Fig.2][Fig.3] Figures 1 to 3 schematically illustrate in perspective steps of manufacturing a device comprising flush metal tracks, according to an embodiment of the present invention.

[0018] [Fig.4] [Fig.4] illustrates an annealing diagram for forming the metal tracks of the device, according to an embodiment of the present invention.

[0019] [Fig.5] [Fig.5] schematically illustrates a support having a curved surface, according to an embodiment of the present invention.

[0020] [Fig.6] [Fig.6] schematically illustrates in perspective a flat support comprising hollow reliefs, according to an embodiment of the present invention.

[0021] [Fig.7] [Fig.7] schematically illustrates in perspective a device comprising the flat support illustrated in [Fig.6], in which metal tracks are formed at the level of the hollow reliefs, and on which electronic chips and a capacitor are mounted, according to an embodiment of the present invention.

[0022] [Fig.8] [Fig.8] schematically illustrates in perspective a power module comprising the device illustrated in [Fig.7], and heat sinks, according to an embodiment of the present invention.

[0023] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications. In particular, on the schematic diagrams, the thicknesses of the different layers and portions, and the dimensions of the patterns and reliefs are not necessarily representative of reality. DETAILED DESCRIPTION

[0024] Before beginning a detailed review of embodiments of the invention, optional features which may possibly be used in combination or alternatively are set out below:

[0025] According to one example, the support is made from ceramic.

[0026] According to one example, the production of the ceramic-based support is completely carried out before filling the at least one relief, without any subsequent step after filling. The additive manufacturing of the ceramic support is completed before filling the hollow reliefs. The additive manufacturing of the ceramic support does not require any further manufacturing steps after filling the reliefs has begun.

[0027] According to one example, the method further comprises polishing the face of the support, for example chemical-mechanical polishing, after annealing the metallic ink. This makes it possible to improve the flatness of the face of the support and / or the leveling of the metallic ink with the face of the support in proximity. This makes it possible to improve the surface condition of the face of the support and / or the exposed surface of the metallic ink, for example for subsequent soldering of an electronic chip on the metallic tracks.

[0028] According to one example, the filling of the at least one recessed relief and the scraping of the face of the support are carried out simultaneously in a single step. This saves one step. Such an embodiment is particularly advantageous for forming thin metal tracks in the support. A scraper is typically used to spread the metallic ink and to scrape and equalize the level of metallic ink in the recessed reliefs. A front of metallic ink moves in front of the scraper and is partly deposited in the recessed reliefs. The metallic ink is removed from the face of the support behind the scraper. The metallic ink remains only in the recessed reliefs of the support.

[0029] According to one example, the filling of the at least one hollow relief comprises a first pre-filling step before scraping the face of the support. This makes it possible to pre-fill the hollow reliefs, in particular when a large thickness of metal is required to form the metal tracks.

[0030] According to one example, the filling of the at least one hollow relief comprises a second filling step during the scraping of the face of the support, after the first pre-filling step. The filling is completed during the second step. The topping up is typically done during the scraping, by pushing the ink front me- metal in the partially filled hollow reliefs.

[0031] According to one example, the first pre-filling step is done by localized dispensing with an ink jet.

[0032] According to one example, the method further comprises a conventional screen printing step, through a screen printing mask, typically after filling and scraping. This makes it possible to increase the metallization thickness.

[0033] According to one example, the metallic ink is silver-based. Such metallic inks are commercially available, as standard. This makes it possible to reduce the cost of the process. The viscosity of the metallic ink can be chosen according to the dimensions of the intaglio reliefs, their form factor and / or the flatness of the face of the support.

[0034] According to one example, the face of the support has a curved surface and the scraping of the face of the support is configured to follow this curved surface. The face may have a continuous curvature, a linear slope or a slope break. The scraping may be advantageously adapted to different support profiles, for example to produce three-dimensional devices.

[0035] According to one example, the metal tracks are configured to be connected to an electronic chip. The electronic chip is surface-mounted on the support.

[0036] According to one example, the device is configured to be integrated into a watchmaking or jewelry system. The compactness of the device is improved. The visual rendering, in particular via the reflection properties of the “hybrid” ceramic / metal face of the support comprising the flush metal tracks, is improved.

[0037] Unless incompatibility exists, it is understood that all of the above optional features may be combined to form an embodiment that is not necessarily illustrated or described. Such an embodiment is obviously not excluded from the invention. The characteristics and advantages of the method according to the invention may apply, mutatis mutandis, to the characteristics and advantages of the device or system according to the invention, and vice versa.

[0038] It is specified that, in the context of the present invention, the terms "on", "overcomes", "covers", "underlying", "facing" and their equivalents do not necessarily mean "in contact with". Thus, for example, the deposition or formation of a first layer on a second layer does not necessarily mean that the two layers are directly in contact with each other, but means that the first layer at least partially covers the second layer by being either directly in contact with it, or by being separated from it by at least one other layer or at least one other element.

[0039] A layer may also be composed of several sub-layers of the same material or of different materials.

[0040] A substrate, a stack, a layer, an element “based” on a material A, is understood to mean a substrate, a stack, a layer, an element comprising this material A only or this material A and possibly other materials, for example alloying elements and / or doping elements.

[0041] A preferably orthonormal reference frame, comprising the axes x, y, z is shown in the attached figures.

[0042] In the present patent application, the thickness of a layer is taken along a direction normal to the main extension plane of the layer. Thus, a layer typically has a thickness along z. The relative terms "on", "overcomes", "under", "underlying", "intercalated" refer to positions taken along the z direction.

[0043] The terms "vertical", "vertically" refer to a direction along z. The terms "horizontal", "horizontally", "lateral", "laterally" refer to a direction in the xy plane. Unless explicitly stated, thickness, height and depth are measured along z.

[0044] An element located "perpendicular" or "straight" to another element means that these two elements are both located on the same line perpendicular to a plane in which a lower or upper face of a substrate mainly extends, that is to say on the same line oriented vertically in the figures.

[0045] Additive manufacturing is also referred to as 3D printing in the following, as a synonym.

[0046] In the context of the present invention, the metallic ink is typically a screen printing ink. It has a viscosity compatible with the implementation of a standard screen printing process. As such, the metallic ink can also be considered as a metallic “paste”.

[0047] In the context of the present invention, the term "equalize" means "bring to the same level". The level of metallic ink in the at least one hollow relief thus has, after equalization, substantially the same level as the face of the support bordering said at least one hollow relief. The free surface of the metallic ink extends as an extension of the face of the surrounding support. The equalization of the levels is understood to be within manufacturing tolerances. Thus, depending on the surface tension of the metallic ink, the free surface of the metallic ink may have a slight curvature projecting or hollowing from the face of the support. This free surface may also change during subsequent annealing. Those skilled in the art understand that scraping typically makes it possible to equalize the levels during the passage of the scraper, without prejudging the actual level of the ink after scraping.

[0048] Similarly, the term "flush" is understood to mean within manufacturing tolerances, and encompasses slight variations in levels between the face of the support and the surface of the metal track formed after annealing.

[0049] The terms "substantially", "approximately", "of the order of" mean to within 10%, and preferably to within 5%. Furthermore, the terms "between ... and..." and equivalents mean that the limits are included, unless otherwise stated.

[0050] [Fig.l] illustrates a ceramic support manufactured by 3D printing according to one embodiment of the method. This support 10 has an upper face 100 and comprises reliefs 12 recessed with respect to the upper face 100. The reliefs 12 recessed may be in the form of grooves, holes, grooves, cavities or notches for example. The support may be based on ceramic for example based on alumina or aluminum nitride. 3D printing advantageously makes it possible to directly produce the reliefs 12 recessed in the support 10, typically without removing material. The support 10 then forms a mold for metal patterns or tracks.

[0051] [Fig.2] illustrates a filling of the reliefs 12 of the support 10 by applying a metallic ink 21 using a scraper 30 on the upper face 100 of the support 10. The metallic ink 21 is accumulated at the level of the beveled end 31 of the scraper 30, and pushed into the reliefs 12 during the movement of the scraper 30 along x. The metallic ink front 21 pours into the hollow reliefs 12 as the scraper moves along x on the upper face 100 of the support. The end 31 of the scraper 30 is typically in contact with the upper face 100. This makes it possible to prevent the metallic ink 21 from remaining on the face 100 of the support. The scraper 30 allows both filling in hollow reliefs and removing excess metallic ink.

[0052] As illustrated in [Fig.3], after the scraper has passed, the surface 200 of metallic ink filling the hollow reliefs is substantially at the same level as the face 100 of the support 10. This filling technique with a scraper is similar to “maskless” screen printing. It is the support 10 which directly forms the mold in which the metallic ink is deposited. It is not necessary to provide a mask dedicated to the formation of the metal track patterns, unlike conventional screen printing.

[0053] The metallic ink has fluidic properties, typically viscosity and surface tension, compatible with this scraper spreading technique. It also has good adhesion power with the support 10, typically with ceramics. It may comprise metallic nanoparticles, for example silver nanoparticles. The metallic ink may be chosen from standard metallic screen printing inks, for example a silver-based metallic ink from the Dycotec references DM-SIP-14001S or DM-SIP-14033. Other metallic ink formulations are conceivable, depending on the intended applications.

[0054] The filling of the reliefs 12 can be done in a single step, as illustrated in Figures 2 and 3. The filling and the scraping are done here simultaneously. This method of rea lization is well suited for filling shallow recessed reliefs, typically for depths less than or equal to 500 pm. For greater depths, pre-filling of the recessed reliefs can be carried out. This pre-filling can be done by inkjet type dispensing, via a nozzle for example. The pre-filling can then be completed by scraper filling as described previously.

[0055] After filling and equalizing the levels of metallic ink with the upper face of the support, a densification heat treatment is typically carried out. This heat treatment makes it possible to evaporate the solvents of the metallic ink and / or sinter the metallic nanoparticles to form the metallic tracks or patterns 20 ([Fig.3]).

[0056] [Fig.4] illustrates an example of heat treatment recommended for Dycotec metallic ink references. This heat treatment typically corresponds to a stabilized annealing at approximately 850°C for ten minutes, with controlled temperature rise and fall.

[0057] After annealing, an optional polishing step can be performed. Polishing the upper face 100 of the support, for example chemical-mechanical polishing or polishing with a diamond disc, can advantageously flatten the face 100 of the support when it is not perfectly flat. Polishing can also make it possible to remove any silver paste residue outside the defined cavities and / or to level the metal tracks. A perfectly flat surface, with well-defined flush metal tracks, is thus advantageously obtained. Other post-annealing steps can also be performed, for example to prepare the surface of the metal tracks for subsequent soldering of components on said metal tracks. A chemical etching or a plasma can for example be carried out.

[0058] Figures 5 and 6 illustrate other configurations of support 10 manufactured by 3D printing. 3D printing advantageously makes it possible to manufacture a support having a non-planar upper face 100, typically a curved face 100 ([Fig.5]). In this case, the application of the scraper for filling and / or for scraping can advantageously follow the curvature(s) of the face 100. A device comprising a support and metal tracks flush with a curved face of the support can thus be advantageously obtained.

[0059] [Fig.6] illustrates a support 10 for a power electronics test vehicle. This support is made of ceramic by 3D printing, as previously, so as to provide hollow reliefs 12 opposite the face 10 of the support.

[0060] [Fig.7] illustrates the mounting of different components on the support 10, after rea lization of the metal tracks 20 by the method according to the invention. The terminals 40, the chips 41 and the capacitor 42 are mounted, for example by soldering, on the metal tracks 20 flush with the surface of the support 10. The electrical insulation is thus improved. The compactness of the test vehicle is also improved.

[0061] [Fig.8] illustrates the IM power module made from the test vehicle on which one or more heat sinks 50 are assembled.

[0062] It is clear from the above that the method according to the invention advantageously makes it possible to produce a device comprising a support and metal tracks buried in said support, having a free metal face flush with the face of the support. Such a device is particularly advantageous for limiting electrical insulation defects or partial discharges in power electronics modules. Such a device also requires fewer materials for manufacturing and less energy for operation. The energy and environmental impact of such a device is therefore advantageously reduced.

[0063] Other applications are conceivable, particularly in the field of metallization of ceramics. Watchmaking or jewelry systems can advantageously take advantage of such a device. The invention is not limited to the embodiments previously described.

Claims

Claims

1. Method for producing a device comprising a support (10) and at least one metal track (20) flush with a face (100) of said support (10), said method successively comprising: • Producing the support (10) by additive manufacturing, by providing in the support (10) at least one relief (12) hollow with respect to the face (100) of the support (10), said at least one relief (12) being intended to receive the at least one metal track (20), • Completely filling the at least one relief (12) hollow with a metallic ink (21), • Scraping the face (100) of the support (10) so as to equalize a level of metallic ink (21) in the at least one relief (12) hollow with the face (100) of the support (10) bordering said at least one relief (12) hollow, • Annealing the metallic ink (21) so as to form at least one metal track (20) flush with the face (100) of the support (10).

2. Method according to the preceding claim, wherein the support (10) is made of ceramic.

3. Method according to the preceding claim, wherein the making of the ceramic support (10) is completed before filling the at least one recess (12), without any subsequent filling step.

4. Method according to any one of the preceding claims, further comprising polishing the face (100) of the support (10) after annealing the metal ink (21).

5. Method according to any one of the preceding claims, wherein the filling of the at least one recess (12) and the scraping of the face (100) of the support (10) are carried out simultaneously in a single step.

6. Method according to any one of claims 1 to 5 in which the filling of the at least one hollow relief (12) comprises a first pre-filling step before scraping the face (100) of the support (10).

7. Method according to the preceding claim in which the filling of

8.

9.

10. the at least one hollow relief (12) comprises a second filling step during scraping of the face (100) of the support (10), after the first pre-filling step. Method according to either of the two preceding claims in which the first pre-filling step is carried out by localized dispensing with an ink jet. A method according to any preceding claim wherein the metallic ink (21) is silver based. A method according to any preceding claim wherein the face (100) of the support (10) has a curved surface and the scraping of the face (100) of the support (10) is configured to follow this curved surface.

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